『Abstract
　Characterization of the vertical distribution of geochemical element concentration is essential for economic planning in the mining industry. 10 mineralized boreholes and 1 non-mineralized borehole from the Qulong copper deposit, Tibet, western China, were collected to identify the vertical distribution properties of Cu values using fractal models. The vertical distribution of Cu values in mineralized and non-mineralized boreholes shows a positive skewed distribution in the former and multimodal distribution in the latter. The results obtained by the box counting method show that the vertical distributions of Cu values in mineralized and non-mineralized boreholes exhibit self-similarity with box dimensions ranging from 1.28 to 1.37. The box dimensions of mineralized boreholes are greater than that of Cu values in the non-mineralized borehole, indicating that the mineralization makes the distribution of Cu values more irregular. The power-law frequency analysis reveals that Cu values in mineralized boreholes are bifractal. The two portions of the plot define a crossover point at 0.33％, for Cu values less than and greater than 0.33, fractal dimensions range from 0.1 to 0.65, in non-mineralized rocks, and range from 2.71 to 5.79, in the mineralized rocks. Hurst exponents for mineralized boreholes occur at 0.8, which are greater than 0.5, indicating that Qulong copper deposits has a good continuity of mineralization.

Keywords: Fractal; Box dimension; Power-law frequency; Hurst exponent; Borehole; Qulong』

1. Introduction
2. Fractal models
　2.1. Box counting method and box dimensions
　2.2. Power-law frequency model
　2.3. Hurst Exponent
3. Geological setting and sampling
4. Results and discussions
　4.1. Frequency distribution of Cu
　4.2. Box dimensions
　4.3. Power-law frequency distribution of Cu values
　4.4. Hurst exponents
5. Conclusions
Acknowledgements
References